Method of tensioning the strings in a racquet

ABSTRACT

A method of stringing a racquet includes independently tensioning a plurality of strings in the racquet and maintaining the independent tensioning. Individual strings are held and their tensioning maintained using cleats and grommets. In this fashion, the elastic properties of the shorter strings may be matched to that of the longer strings, giving a larger sweet spot. The strings may be manufactured as a pre-woven mesh.

The present invention relates generally to improvements in sportingracquets and, more particularly, but not exclusively, to improvements inmethods of stringing racquets, sporting racquets with improved stringingand tools and machines for stringing and improving the stringing ofsporting racquets.

Currently available sporting racquets, for example tennis racquets, arecontinuously strung by passing a length of stringing material throughholes in a frame, pulling the length of stringing material to apredetermined pressure and tying it off under pressure against itself.The pressure is retained within the length of stringing material.Conventionally, a single length of stringing material forms stringswhich run length-wise in the racquet head and a separate single lengthof stringing material forms strings which run cross-wise.

Because of this stringing method, the tension of each string in theracquet (the term "string" being used herein to mean one string "span"from one side of the racquet head to the other, and not the total lengthof stringing material) is substantially similar across the entireracquet face (the term "racquet face" being used herein to mean thestrung area of the racquet head). The "elastic quality" of a tensionedstring depends upon the tension applied and the length of the string.The amount of "elastic bend back" experienced by a relatively longstring in a conventional racquet head when an object is struck will begreater than that available to the shorter strings in the racquetbecause all the strings are at substantially similar tension i.e., theelastic properties vary in dependence on the length of the string. Thiscan have a deleterious effect on shot playing. For example, it is wellknown that in tennis it is desirable to strike the ball at the centrearea of the racquet face, to ensure that the ball travels in the desireddirection with the desired power. At the centre area of the face of aconventionally strung tennis racquet the strings will have similarelastic properties, by virtue of the fact that the length differencesbetween strings are at a minimum. This centre area is generally known asthe "sweet spot".

At the outer area of the racquet face the shorter and longer stringswill have different elastic properties. It is well known that controland power applied by the outer area of the racquet face of aconventional tennis racquet is extremely unreliable. Hence thedesirability of striking a ball with the centre of the racquet face.

Even towards the centre of the racquet face in the so-called "sweetspot", the elastic properties of the strings vary somewhat.

In presently available sporting racquets, therefore, a perfect sweetspot does not exist and the nearest approximation to a sweet spot islocated in a small area, generally towards the centre of the racquetface.

From a first aspect, the present invention provides a method ofstringing a racquet, comprising the steps of independently tensioning atleast a plurality of strings in the racquet and applying means formaintaining the independent tensioning.

By "independently tensioning" is meant the application of tensionindependently to each string of at least the plurality of strings.

The plurality of strings are preferably independently tensioned todifferent tensions and the resultant differential pressures betweenstrings maintained.

Preferably, all strings in the racquet will be independently tensioned,although embodiments are envisaged where some of the strings may bestrung by prior art methods and the others independently tensioned.

In at least preferred embodiments, the ability to independently tensionstrings to different tensions and maintain the resultant differentialpressures between strings can result in vast improvements in racquetquality. It is possible to provide a racquet face where the elasticquality is substantially even over the entire face. In other words, itis possible to provide a racquet which has a "sweet spot" acrosssubstantially the entire racquet face.

The ability to individually control tension also allows "zoning" of theracquet face. Different areas of the racquet face may display differentqualities.

It is also possible to use different gauge and/or material strings indifferent areas of the racquet face to assist variation or providefurther variation in racquet characteristics.

A "sweet spot" over the entire area of a racquet will generally beachieved by having the tension in the longest strings the greatest,stepping down the tension for shorter strings. For example, where thetension in the longest strings (the base tension) is 28 kg, then thetension in the shorter strings is set lower, say 26, 24, 22, 18 etc.,depending upon their relative length with respect to the length of thelongest string. We have found that stepping down, or providingdifferential tensions between the strings in this manner provides thebest method of obtaining even elastic quality over the entire surface ofthe racquet.

From a second aspect, the present invention provides a method ofstringing a racquet, comprising the step of tensioning at least aplurality of strings in the racquet in accordance with the followingformula: ##EQU1## wherein,

T_(s) is the tension to be applied to the particular string beingtensioned, L_(s) is the length of the particular string being tensioned,L_(L) is the length of the longest string in the racquet, T_(L) is thetension of the longest string in the racquet which is preset as thestandard or base tension and P is in the range 1.7 to 2.3 inclusive.

In one preferred embodiment, P=2.

We have found that tensioning strings in accordance with this formulaleads to elastic quality of the strings so tensioned being substantiallysimilar. Where all the strings on a racquet are tensioned in thismanner, this, in at least preferred embodiments, leads to a "sweet spot"over substantially the entire face of the racquet.

P=2.3 has also been used with good effect. P in the range 1.7 and 2.3may be used to provide racquets of good quality, in at least preferredembodiments.

The length of each string L, is preferably measured between the insidefaces of the racquet frame, in each case.

It will be appreciated that other formulas may be devised and applied toprovide racquets with different characteristics.

From a third aspect, the present invention provides a method ofstringing a racquet, comprising the step of applying tension to at leasta plurality of strings in the racquet so that the elastic quality of aplurality of the shorter strings substantially matches the elasticquality of a plurality of the longer strings.

As discussed above, where the elastic quality of shorter and longerstrings in a racquet substantially matches, then the elastic bend backresponse of the racquet will be substantially even across the face ofthe racquet, providing more precise control/power characteristics overthe racquet face than available in conventional, prior art racquets.

From a fourth aspect, the present invention provides a method ofstringing a racquet, comprising the step of tensioning at least aplurality of the strings to a predetermined level so that at least aplurality of strings retain different, pre-calculated tensions, in orderto provide predetermined elastic qualities for the strings, whereby toproduce racquets having predetermined qualities.

Preferably, the pre-calculated tensions are calculated to providepredetermined racquet characteristics, i.e., power, spin and directionof shot provided by racquet. As discussed above, it is possible toindividually tension the racquet strings to tensions which arecalculated to provide a sweet-spot over the entire racquet face.

As also discussed above, any characteristic may be applied in accordancewith this method. For example, different areas of the racquet may havedifferent qualities i.e., some may be more useful for applying spin,some more useful for applying power and direction, depending generallyupon the elastic properties of a particular area.

From a fifth aspect, the present invention provides a method ofstringing a racquet, comprising the steps of tensioning at least aplurality of strings against a holding means associated with theracquet, by individually adjusting the tension in each of the pluralityof strings to a predetermined level, by applying more or less pressureto each individual string with respect to the holding means, and whenthe string has been adjusted to the predetermined tension level, lockingthe string with respect to the holding means, so that the string is heldat a predetermined tension level against the holding means.

Preferably, the plurality of strings is tensioned so that they havedifferent tensions from each other, and the holding means is arranged tomaintain the difference in tension (differential pressure betweenstrings). The strings may be individually strung, i.e., one string foreach string travel across the face of the racquet, or continuouslystrung as in the prior art, i.e., a single length of stringing materialforming a plurality of string spans across the face of the racquet.

By "adjusting the tension" is meant the calibration action of making thetension greater or lesser in a string until arriving at a predeterminedtension. In preferred embodiments, this will mean stretching or relaxingthe string with respect to the position of the holding means which willgenerally be stationary with respect to the racquet frame. A calibrationtool (see later) may be utilised to adjust the tension in the strings.

In one preferred embodiment, the holding means comprises a plurality ofcleats. Preferably, each individual string is held between a pair ofcleats. The cleats are preferably seated within the racquet frame,within a grommet strip which extends into the string holes and mountsthe cleats. In an alternative embodiment, each cleat is provided with aplurality of projections which extend outwardly to maintain the positionof the cleat within the string hole.

The cleat has teeth which narrow downwardly from a relatively wideopening. A string is passed through the opening, adjusted to tension andthen locked with respect to the cleat by being pushed downwardly towardsthe narrow part of the cleat teeth.

By utilising a pair of cleats at opposite sides of the racquet frame toadjust the tension of a string extending between the pair of cleats, itis possible to apply "individual stringing", i.e., a single length ofstringing material for each of the plurality of strings. In oneembodiment of the present invention, after the string has been tensionedand locked between a pair of cleats, a "tail", or length of string isleft projecting from one or both of the pair of cleats, outwardly of theracquet frame. This tail enables subsequent re-adjustment of the tensionin the string, as required. Preferably, the tail or tails will beprotected by a removable cover extending about the frame of the racquet.

Further, mounting a string between a pair of cleats allows theapplication of tension to the string from either end, and not just fromone end of the string as in the prior art. In the prior art, the tensiontends to be greater towards the end of the string where tension has beenapplied and lesser towards the end where tension is not applied. Byapplying tension to either end of the string, this tension differentialalong the length of the string is minimised. It will be appreciated thatit is possible to apply tension from one end of the string only, ifrequired.

In a preferred embodiment a pair of cleats is provided for each stringin the racquet, allowing the tension for all strings in the racquet tobe individually adjusted.

In an alternative embodiment, the holding means comprises a lockingcross-section grommet strip associated with the frame of the racquet,into which the strings may be locked. In particular, the grommet strippreferably comprises a strip having a "V" cross-section slot runninglengthwise of the strip. The "V" section slot preferably extendssubstantially between adjacent string holes on the outer surface of theracquet frame. In a preferred method utilising this particular holdingmeans, continuous stringing is employed. The tension in a first stringis adjusted to the required level and then the string length at the endof the string is passed into the "V" section grommet strip, through theadjacent string hole and across to the other side of the racquet to formthe adjacent string. The "V" section grommet strip maintains thedifferential pressure between the first string and the adjacent string,by virtue of gripping the string length and preventing it from slidingback under tension. The "V" section groove may be toothed or serrated.

A further alternative embodiment utilises high-friction pads againstwhich the tension of individual strings may be maintained, preferably ina continuously strung racquet. The method of utilising high-frictionpads as the holding means is similar to the method employed utilisingthe "V" section grommet strip. Each high-friction pad essentially actsto maintain a differential pressure between adjacent strings in theracquet. High friction pads could be incorporated into the grommet stripor could be part of a continuous grommet strip.

Alternative embodiments may utilise metal inserts inserted in a grommetstrip in order to grip the strings. The metal inserts may be toothed orserrated.

A further alternative is to have the grommet strip comprised of a highfriction material where the string has to be gripped and a lowfrictional material where the grommet passes into the string hole in theframe.

In a further alternative, a continuous grommet strip of high frictionmaterial is used to maintain differential pressure between strings in acontinuously strung racquet. The strings contact the high frictionalmaterial where they extend on the outer surface of the frame and aresubstantially prevented from slipping back under tension by theresistance provided by the high frictional material of the grommetstrip.

Note that in the grommet strip and high-friction pad method tension of astring may slip back somewhat when the length of string is beingmanipulated to form adjacent strings. This should preferably be takeninto account when considering the tension level to initially adjust thestring to. For example, in some cases it may be prudent to adjust thetension to a level somewhat higher than the predetermined tension levelrequired, to take "slip back" during stringing into account.

In a further alternative, the holding means may comprise a combinationof the embodiments discussed above e.g., combination of cleats andmodified grommet strip is one frame.

In a further alternative embodiment, the holding means preferablycomprises a racquet frame which is manufactured directly onto stringswhich have been pre-tensioned to provide the desired racquetcharacteristics. The racquet frame itself therefore locks the stringswithin the frame and maintains the predetermined tension.

Note that it is accepted that with the present invention, as withconventional racquets, tension of the strings is likely to reduceovertime and as the racquet is used in play. All the statements givenabove and below defining the alternative aspects of this inventionshould be read with this in mind. In at least some embodiments of thepresent invention, it is possible to readjust the tension of thestrings. In particular, in the cleat embodiment where adjustment oftension is possible by removing the string from the cleat or cleats,re-tensioning and reapplying to the cleats. Restringing is also possiblein some embodiments, as with conventional racquets.

Note that in an alternative embodiment, a locking cross-section grooveor high friction surface may in fact be an integral part of the racquetframe and not formed within or by a separate grommet strip.

Further, in the cleat embodiment, rather than the cleat being a separatebody mounted with respect to the racquet frame, it is also envisagedthat cleats could be formed integrally with the racquet frame. Thiswould be particularly suited to racquets of graphite and aluminum.

In any of the aspects of the invention discussed above and below,strings may be individually tensioned to provide predeterminedcharacteristics for the racquet. Tensioning may be applied so that theelastic properties are uniform over the face of the racquet, providing asweet spot over the entire face, or may be applied to provide varyingcharacteristics over the face of the racquet, e.g., one area may providea power zone, another area a spin zone, etc. Further, string gauges andmaterial types may be varied within a single racquet head in order toassist in providing predetermined qualities for the racquet. Further,the racquet may be strung by a mixture of continuous stringing andindividual stringing, individual stringing only or continuous stringingonly, again to assist with variation in the racquet characteristics.

It should be noted that throughout the specification and claims the term"racquet" should also be taken to cover racquet heads which may bemanufactured separately from a shaft to be subsequently married with ashaft to provide the complete racquet. The present invention includeswithin its scope replacement racquet heads which are removable from theracquet shaft.

From a sixth aspect, the present invention provides a sports racquet,strung in accordance with the method of any of the aspects discussedabove.

The racquet in accordance with this aspect of the invention may bestrung in accordance with any of the techniques discussed above.

From a seventh aspect, the present invention further provides a sportsracquet frame, including a holding means, arranged to enable individualadjustment of the tension in each of a plurality of racquet strings to apredetermined level and to lock each string with respect to the holdingmeans so that each string is held at the predetermined tension levelagainst the holding means.

The holding means may comprise a plurality of cleats into which thestrings may be locked, a racquet frame formed onto pre-tensionedstrings, a locking cross-section grommet strip around the frame of theracquet into which the string may be locked, a plurality ofhigh-friction pads against which the tension of individual strings maybe maintained, a length of high friction material, or any of the other"holding means" discussed above.

From an eighth aspect, the present invention further provides aminiature cleat for mounting with respect to a racquet frame andarranged to hold a string in the racquet frame at a predeterminedtension.

This cleat may be used in the method and racquet discussed above formaintaining string tension in the racquet. All or most cleat designs maybe used, including all the jamming varieties, V jam, rocker types, anglejam, cam action cleats, etc.

A preferred cleat type is a V jam type including a plurality of teethwhich are, in use, angled outwardly against the pressure exerted by thestring.

The cleats are preferably mounted within a grommet strip which extendsaround the racquet frame. The grommet strip may not be an entire strip,but a plurality of separate grommets, e.g., one grommet associated witheach hole.

The cleats may be provided with protrusions on their outer surface whichassist in retaining the cleat within the grommet strip.

From an ninth aspect, the present invention provides a grommet stripmounting a plurality of miniature cleats, the cleats being in accordancewith the preceding aspect of the invention.

The present invention yet further provides a kit-of-parts, comprising aplurality of miniature cleats as discussed above and a grommet strip formounting the cleats with respect to a racquet frame so that the cleatsmay be arranged to apply and maintain a predetermined tension to racquetstrings.

The present invention yet further provides a grommet strip, for use witha racquet frame and including a locking cross-section groove toindependently hold at least a plurality of racquet strings atpredetermined tensions.

The locking cross-section groove is preferably arranged to maintain adifferential pressure between adjacent strings in a continuously strungplurality of strings.

The present invention, in at least preferred embodiments, provides theability to individually tension each string of a plurality of strings ina sporting racquet to different tensions and to maintain the differenttensions between strings. For at least some embodiments, this enablesthe use of pre-woven string sets (comprising a plurality of interwovenlengths of stringing material--one length for each string) for racquetstringing, as the strings no longer have to be continuously strung as itis possible (in at least some embodiments) to have a single length ofstringing material comprising each string span across the face of aracquet (independent stringing).

In a method of manufacturing a racquet in accordance with the presentinvention utilising a pre-woven string set, the string set is placedwithin a racquet head with the individual ends of strings extendingthrough the string holes in the racquet frame. Tension is then appliedin a predetermined manner to each string and maintained by holdingmeans, preferably cleats.

In one alternative embodiment, predetermined tensions will be applied toindividual strings in a string set and a racquet frame moulded to holdthe strings at the predetermined tension.

The strings may be tensioned by being pulled from either end, in orderto reduce variability across the length of the string (see above), ormay be tensioned by pulling from one end.

From a further aspect, the present invention provides a method ofmanufacturing a pre-woven string mesh for sporting racquets, comprisingweaving a plurality of strings together in a weaving loom, in acontinuous stream, applying securing means to hold the weave inposition, and cutting the weave to a shape to fit into a racquet head.

The securing means preferably comprises webbing, preferably plasticswebbing, applied to each face of the weave. A low tack adhesive sheet orself adhesive film may be used as the webbing.

The present invention yet further provides a pre-woven string mesh forsporting racquets, comprising a plurality of strings woven together andguillotined to a racquet shape, and maintained in position by a securingmeans comprising webbing applied to each face of the weave.

In prior art stringing methods, which employ continuous stringing, ithas previously been necessary to provide bracing for the top and bottom,left and right sides of the racquet frame, in order to prevent the frameimploding during the stringing operation, i.e., if all the verticalstrings are strung before any of the horizontal strings, the pressure onthe racquet is likely to be so great as to cause the racquet to implodein the vertical direction.

The ability to independently apply tension to each string in the racquetand/or to independently string the racquet, in accordance with aspectsof the present invention, means it is possible to provide a stringingmethod which requires no bracing of the racquet frame. The strings maybe tensioned in the order which creates the least stress on the racquetframe.

By choosing a suitable order for tensioning the strings, bracing meansto support the racquet frame during stringing can be avoided. This isparticularly convenient for individually strung racquets.

In some racquet embodiments, racquets may be specially marked toindicate in what order the stringing tool needs to be applied to thestrings in order to tension them.

A further problem with prior art continuous stringing techniques is thatit is necessary to manufacture the racquet frame so that portions of theframe are stronger than other portions, i.e., "strong zones" of theframe are provided, in order to support the stresses produced by thecontinuous stringing to even tension for all strings.

In the present invention, because it is possible to individually tensionstrings, it is possible to dispense with at least some of the strengthzones in the racquet frame, particularly where a racquet is strung suchthat only the longer strings are tensioned to high pressures.

From a further aspect, therefore, the present invention provides aracquet, the frame being designed to support stringing strung inaccordance with the present invention and dispensing with or varying theposition/strength of at least some strength zones in the frame.

The frame may be altered to produce different playing characteristics inthe frame. Weight may be loaded in different parts of the frame,depending upon player preference or to provide particularcharacteristics to the frame. Tension of the strings can be individuallyadjusted to take into account the weight distribution in the frame.

As discussed above, different pressure patterns in stringing may beapplied in accordance with the present invention. The invention alsoenvisages the production of a racquet frame structure which is designedin accordance with pressure patterns to be utilised in stringing. Thatis, strengths and weaknesses in the frame may be designed to accord withamount of pressure provided by particular areas of the pressure pattern.

In continuously strung prior art racquets, the general stringingtechnique involves stringing with a single continuous length ofstringing material, or two continuous lengths of stringing material (onefor the verticals and one for the horizontals), then tying off theindividual length of stringing material under pressure, so that thepressure on the individual strings is exerted against the continuousstring itself.

Apart from the problem that all the strings in such a racquet are underthe same tension and therefore the characteristics provided by theracquet are not ideal, there is a further problem, in that on tying offthe continuous string much of the tension which has been applied to thelater tensioned strings during stringing is lost (upwards of 30% of theapplied tension may be lost during tying off). In order to maintainsufficient tension in the later tensioned strings, therefore, it isnecessary to over-tension some strings past the base tension requiredand predict the drop off in pressure due to tying off, in the hope ofachieving the correct pressure in the string.

From yet a further aspect, the present invention provides a method ofsecuring the strings of a racquet, by locking the string or stringswithin a locking member which secures the string and allows minimaldrop-off in tension during the locking process.

Locking means preferably comprises a cleat into which the string can belocked and retained. The cleat is preferably mounted with respect to theracquet frame, preferably within the racquet frame in a string hole.

Where a racquet is continuously strung, only a single, or a pair ofcleats will be required (where the horizontal and vertical strings areformed from one length of string), or three or four cleats where thevertical and horizontal are strung by separate string lengths.

In this aspect of the invention, the strings will be pulled to pressureand locked within the cleat(s).

This aspect of the invention has the advantage that, in at leastpreferred embodiments the amount of pressure lost during the lockingstep is much less than that lost during a tying off step as used in theprior art.

The ability to individually string in accordance with the presentinvention (i.e., not continuously string, but have individual stringlengths for at least a plurality of racquets strings), also allowsdifferent coloured strings to be used for each string. A racquet maythus be designed with a surface pattern. This could be used forsponsorship, advertising, etc. From yet a further aspect, the presentinvention provides a method of presenting information, comprising thestep of stringing a sporting racquet with individual string lengths,each string being marked so that the individual string lengths togetherform a predetermined pattern on the face of the racquet, whereby thepattern may present advertising, sponsorship, etc.

The present invention from yet a further aspect provides a racquetstrung in accordance with the above aspect of the invention.

Features and advantages of the present invention will become apparentfrom the following description of embodiments thereof, by way of exampleonly, with reference to the accompanying drawings, in which:

FIG. 1 is a top view of a portion of a racquet frame in accordance withan embodiment of the invention;

FIG. 2 is a section on 2--2 of FIG. 1;

FIG. 3 is a bottom view of the portion of the racquet frame of FIG. 1;

FIG. 4 is a perspective view of a cleat used in the embodiment of FIGS.1 to 3;

FIG. 5 is a bottom view of the cleat of FIG. 4;

FIG. 6 is a front view of the cleat of FIG. 4;

FIG. 7 is a side view from one side of the cleat of FIG. 4;

FIG. 8 is a back view of the cleat of FIG. 4;

FIG. 9 is a top view of the cleat of FIG. 4;

FIG. 9A is a sectional view of the cleat of FIG. 4, illustrating exampledimensions and angles;

FIG. 9B is a front view of the cleat of FIG. 9a;

FIG. 9C is a top view of the cleat of FIG. 9a;

FIG. 10 is a side sectional view of a portion of a racquet frame,showing a pair of string holes with grommet strip;

FIG. 11 is a section on 11--11 of FIG. 10;

FIG. 12 is a section on 12--12 of FIG. 10;

FIG. 13 is a top view of the portion of the racquet frame of FIG. 10;

FIG. 14 is a side view of a section through a portion of a racquet framein accordance with an embodiment of the present invention, showing aracquet with grommet strip and frictional pad;

FIG. 15 is a section on 15--15 of FIG. 14;

FIG. 16 is a section on 16--16 of FIG. 14;

FIG. 17 is a top view of the portion of frame of FIG. 14;

FIG. 18 is a perspective view of a portion of a racquet frame inaccordance with the embodiment of FIG. 14;

FIG. 19 illustrates a pre-woven string mesh in accordance with anembodiment of the present invention;

FIG. 20 is a schematic partially sectioned view of tennis racquet strungin accordance with the present invention;

FIG. 21 is a view of a pre-woven mesh labelled to indicate a preferredorder of application of tension to the strings in a racquet tensioned inaccordance with the method of the present invention;

FIG. 22 is a side sectional view of a portion of a racquet frame of analternative embodiment of the present invention, with modified grommetstrip;

FIG. 23 is a top view of FIG. 22;

FIG. 24 is a section on 24--24 of FIG. 23;

FIG. 25 is a side sectional view of a portion of a racquet frame inaccordance with a further embodiment of the present invention with analternative modified grommet strip;

FIG. 26 is a section on 26--26 of FIG. 25; and

FIG. 27 is a section on 27--27 of FIG. 25.

FIGS. 1 to 3 illustrate a racquet frame construction in accordance withan embodiment of the present invention which enables racquets to bestrung in accordance with the present invention, by allowing independenttensioning of each of at least a plurality of strings in the racquet.

The figures disclose a portion of a racquet head frame 1, the portionhaving formed therein a string hole 2, through which it is intended thata racquet string is to be passed and held.

It will be appreciated that the entire racquet frame may be of anyconventional racquet shape, and may be formed integrally with a racquetshaft or separately therefrom as an integral racquet head intended forconnection to a racquet shaft. The racquet frame will have a pluralityof holes therein for receiving strings therethrough. Each string hole 2of the racquet frame of this embodiment will have the same structure andcomponentry as disclosed with reference to FIGS. 1 to 3.

A grommet strip 3 is mounted to the outside of the racquet frame andruns entirely around the racquet head. Please note that individualgrommet strips running only between adjacent string holes may be used asan alternative.

At each string hole 2, a portion 5 of the grommet strip extends withinthe string hole 2. The portion 5 is provided with portions 6 which seatthe cleat 7 within the string hole in a manner most clearly shown inFIG. 2. The cleat 7 has three sets of teeth 8 leaning forwardly from thebase of the cleat 9 towards the outer surface of the racquet frame 1.Four or more teeth may be required to hold lighter tensions.

A further alternative is to have individual "eyelets" for each stringhole, supporting a mounting means for mounting a cleat within the hole.The mounting means will be preferably comprise, an eyelet with a portionextending into the string hole, similar to portion 5 of the illustratedgrommet strip.

The form of the cleat is clearly shown in FIGS. 4 through 9. The teeth 8are arranged to narrow in a generally "V" shape, from a mouth 10 to abase 9. A string may be passed into the mouth 10 and "locked" by beingmoved down the V-shaped cleat towards the base 9 until jammed betweenthe teeth 8. In the preferred embodiment, the cleat 7 is "self-locking".In other words, after the string, passed through the open mouth of thecleat, has been adjusted to tension by a gripping member which holds anend of the string and pulls it to tension, on release of the grippingmember the teeth 8 automatically grip the string and the tension of thestring causes it to slide into the narrow part of the cleat and lockthere. It is not necessary to physically push the string into the narrowpart of the cleat, it happens automatically.

This "micro cleat" may be obtained from Clamcleats Limited, Watchmead,Welwyn Garden City, Hertfordshire AL7 1AP, England.

FIGS. 9A through C show an example of a preferred embodiment of a cleat,showing example dimensions and teeth angle. This example is for thepreferred embodiment only. It will be appreciated that dimensions ofcleats may be varied, depending upon string sizes, racquet frames, etc.

In the embodiment shown, the cleat has three sets of teeth. The numberof teeth may be varied. In particular, where it is necessary to hold astring under a relatively low tension, only two sets or even one set ofteeth may be provided. In general, the more teeth, the more tension thecleat is able to hold. It is envisaged that in a single racquet whereall the strings are tensioned in this manner, the high-tension (usuallylonger) strings may be tensioned by cleats with three teeth, and lowertension strings may be held by cleats with lower numbers of teeth.

Each cleat is mounted within the grommet strip as shown in FIG. 2, withthe teeth 8 leaning outwardly from the base towards the outside of theracquet frame 1. The cleat 7 is held within portion 6 from the section 5of the grommet strip 3 which extends within the string hole 2. Thegrommet strip 3 may be of rigid plastics or other suitably rigidmaterial for maintaining the cleat 7 seated within the hole.

In the preferred embodiment, the portion 5 of the grommet strip willextend downwardly through the string hole to the inner surface of theracquet frame and will form an eyelet about the string hole at the innersurface of the racquet frame. This eyelet prevents the string fromrubbing against the racquet frame and being cut by the racquet frame,which can be a particular problem with graphite and other hard-materialracquet frames.

Further, in the preferred embodiment, the portion 5 of the grommet stripis slightly hollowed on the side of the open portion of the cleat, toenable the string to be easily passed through the string hole and themouth of the cleat.

In an alternative embodiment (not shown), the cleat may have projectionsformed integrally therewith for maintaining the cleat seated in the holewithout any grommet strip portion 5.

In a further alternative embodiment, particularly suited for aluminiumand graphite racquets, cleats may be integrally formed with the racquetframe itself, i.e., integrally formed within string holes in the racquetframe.

In the preferred embodiment, a cleat is associated with every stringhole in the racquet and each string in the racquet is supported andtensioned between a pair of cleats.

In one stringing method, a first end of a string is seated within thefirst of the pair cleats so that it seats firmly within the teeth 8. Thestring is passed through the opposite of the pair of cleats and is thenpulled to the predetermined tension (preferably taking into account anyrelaxation which may occur when the tension is released and before thecleat engages and locks the string). When the tension value is obtained,the means gripping and applying the tension to the string is releasedand the angle of the cleat teeth together with the tension of the stringcauses the string to be gripped by the teeth and drawn within the jawsand locked there. The teeth are arranged not to cut the surface of thestring but in fact to bend the surface of the string. The tension ofeach string in the racquet can thus be determined and set individually.The teeth may cut the outer surface of the string at times withoutcutting all the way through--this may happen at the high tension levels.

With this arrangement individual stringing is preferred.

With this arrangement, strings can be independently tensioned to providepredetermined racquet characteristics. Strings may be tensioned inaccordance with the formula discussed in the preamble in order to give aracquet having a sweet spot substantially entirely over the surfacethereof (where all the strings are tensioned in this manner).Alternatively, the strings may be tensioned to provide predeterminedcharacteristics to predetermined areas of the racquet. The arrangementallows complete flexibility for determining racquet characteristics.Different string gauges, different string materials, etc., may beemployed.

In alternative embodiments, as discussed in the preamble, only some ofthe strings of the racquet may be tensioned using individual holdingcleats as illustrated in the figures. Others could be strung by priorart methods. It really depends on what qualities are required for theparticular racquet.

The provision of a holding cleat also, in at least preferredembodiments, assists with the problem discussed in the preamble relatingto loss of racquet tension due to the necessity to "tie-off" strings, inthe prior art. The cleat may be used in a prior art stringing methodutilising continuous stringing, but instead of tying off the length ofstringing material cleat will be used to retain it. Utilising a cleatwill advantageously reduce drop off of tension, even with prior artstringing methods.

Although the cleat illustrated is the preferred type of cleat, it willbe appreciated that other types of cleats may be employed.

Further, the cleats need not be seated in the string holes, but could beseated on the outer surface of the racquet frame instead.

Conventional racquets may be adapted by widening the string holes toreceive cleats and adding the grommet strip for mounting the cleats.

An alternative method of tensioning the individual strings would be totension each end of a string at the same time and then lock the stringwithin a pair of cleats. This preferably minimises any variation intension over the length of the string.

Where a pre-woven string set is provided (see preamble), apparatus maybe utilised to tension all strings at the same time.

An alternative holding means for allowing independent tensioning ofracquet strings is illustrated in FIGS. 10 through 13. These figuresillustrate a locking cross-section grommet strip arranged to be placedaround the outside of a racquet frame. The grommet strip comprises a "V"shape trench 20 which runs between adjacent string holes 2 in a racquetframe 1. The grommet strip 21 may be a continuous strip, extending aboutthe entire outer circumference of the racquet frame 1, or it may consistof a number of discrete single strips extending between adjacent holes2, or discrete strips extending around holes. The locking sectiongrommet strip may, indeed, merely be an eyelet around each string hole.Most preferably, it consists of a single strip extending around theracquet frame.

As can most clearly be seen in FIGS. 10 and 11, the grommet strip 21incorporates V shaped channel 20 (most clearly seen in FIG. 13) whichruns between the string holes 2.

The locking cross-section grommet strip is intended to facilitate theapplication of independent tensioning to strings in a continuouslystrung racquet and maintenance of differential pressures betweenadjacent strings.

In operation, the length of stringing material will be extended betweena first pair of holes to form a first string and tension applied to thepredetermined tension. The continuous string length is then passed intothe V shaped locking cross-section grommet 20 and into the adjacentstring hole 2 and across to the opposite hole to form the adjacentstring where tension will be, in turn, applied to that string. Thelocking grommet strip section 20 provides a high friction retentionmeans for the continuous string length, which maintains a differentialpressure between adjacent strings. Therefore, if required, differenttensions may be applied to different strings.

As with the previous embodiment, therefore, different characteristicscan be applied to the racquet by adjusting string tension for eachstring.

The locking cross-section may be provided with teeth to increaseretentive capability.

Continuous stringing is preferably utilised in this arrangement. It ispossible to use different string materials, however, by continuouslystringing two or three strings at a time, for example, rather thancontinuously stringing all the strings in the racquet with onecontinuous string. It is therefore possible to vary the gauge andmaterial in the strings, as in the previous embodiment.

FIGS. 14 through 18 show yet a further embodiment which discloses aholding means comprising a pad 30 of high frictional material whichextends between adjacent string holes 2 about the outer surface of aracquet frame 1. The high friction pad 30 is supported on a grommetstrip 31 which extends about the outer circumference of the racquetframe 1. In a similar manner to the "V" cross-section grommet strip ofthe previous embodiment, the high frictional pads 30 extending betweenadjacent holes 2 act to maintain a differential pressure in adjacentstrings strung by a continuous stringing method.

An alternative is to have a grommet strip made of high frictionalmaterial, instead of the smooth plastics used for prior art grommetstrips, the grommet strip passing around the entire outside surface ofthe frame. The high frictional material (any suitable high frictionalmaterial may be used, for example thermoplastic rubbers or EUA) willprevent or at least significantly reduce slip back of differentialpressure between strings.

Note that the grommet strip of the embodiment of FIGS. 10 to 13 couldalso be formed from high frictional material to assist retention ofdifferential pressures between adjacent strings.

FIG. 20 shows a schematic view of a racquet strung in accordance withthe embodiment of FIGS. 14 through 18, with frictional pads. The view ispartially sectioned to show the stringing. The same reference numeralsare used as in the embodiment of FIGS. 14 through 18.

FIGS. 22 through 24 illustrate a further alternative embodimentutilising a modified grommet strip to provide a holding means formaintaining differential pressure between adjacent independentlytensioned strings in a racquet head. Portions 35 of grommet strip 21extend into string holes in the racquet frame 2, as in previousembodiments. As is most clearly seen in figures 23 and 22, part of oneside of the portion 35 is cut away at 61 in the vicinity of the outersurface of the racquet frame 1. A channel 60 is cut in the grommet strip21 extending between adjacent cut-away portions 61 and exposing tovarying degrees the outer surface of the racquet frame 1 betweenadjacent string holes 2. The differential tension (tension applied toeach string in direction 63) between adjacent strings is maintained bythe channel 60 corners 62 acting to grip the stringing material. Inparticular, the differential tension is held by the stringing materialbending around the edges 62 of the frame.

A further alternative holding grommet-strip is illustrated in FIGS. 25through 27. The grommet strip incorporates two separate materials fusedtogether during manufacture. Reference numeral 35 indicates normalgrommet strip material and reference numeral 64 illustrates highfrictional material fused thereto. Reference numeral 65 indicates thefuse join line. As can be seen from reference numeral 66, the highfrictional material may extend, in some variations, into the string hole2.

As shown in FIG. 26, the high frictional material 64 may also include a"V" cross-section groove 20.

FIG. 19 illustrates a pre-woven mesh which lends itself to use with themethod and racquet of the present invention.

The pre-woven mesh 30 is prepared by being woven in large looms byweaving machines which are presently available. The string sets areproduced in a continuous stream, held in position by contact glue orsealed in position by low tack adhesive sheets or other suitable methodstop and bottom of the weave. The weave is then guillotined to racquetshape (slightly larger so that the ends of the guillotined strings willproject through string holes in the racquet frame) and packaged readyfor insertion within a racquet.

In racquet stringing, the free ends of the weave will be placed throughthe strings holes in the racquet from the inside of the frame to theoutside, and the ends can then be pulled to pressure. Preferably, theholding means utilised with the string set in accordance with thisembodiment of the invention will comprise a plurality of cleats, eachstring hole having a cleat, as discussed above in relation to theembodiment of FIGS. 1 to 9.

A predetermined pressure pattern applied in accordance with embodimentsof the present invention may be any desired pressure pattern. Forexample, it may provide a sweet spot over the entire surface of theracquet, by predetermining the tensions of the strings such that theelastic quality of the long strings is the same as the elastic qualityof the shorter strings. Alternatively, different areas of the racquetmay be tensioned to provide different characteristics, one area forspin, one area for power, for example.

The ability to use individual strings in various embodiments of thisinvention enables the possibility that different coloured strings couldbe used to make a predetermined pattern on the face of the racquet. Thispredetermined pattern could be used for advertising, sponsorshippurposes, etc. Each string would be coloured before being inserted intothe racquet, unlike present day pattern making which involves sprayingthe racquet once it has been strung.

One further problem with present day continuous stringing is that it isnecessary to brace the racquet against the tension stress caused by thestrings, in order to prevent implosion of the racquet frame duringstringing. With the present invention, as long as stringing of theindividual strings occurs in the correct order, it is not necessary toprovide a brace, as the strings will compensate for applied pressures.The present invention also provides a marked racquet frame whichindicates the order in which tension should be applied to the strings.

FIG. 21 illustrates the order in which tension may be applied to aracquet in accordance with a preferred embodiment of the presentinvention. Tensioning will be applied consecutively with the illustratednumbering. In at least a preferred embodiment, if tension is applied inthis order, it will not be necessary to brace the racquet, or onlyminimal bracing will be required during stringing. A racquet frame maybe marked with numbers, or colouring, to indicate in what order itshould be tensioned.

Further, prior art continuous stringing requires various strong zones inracquet frames. This adds weight to the racquet. In some embodiments ofthe present invention, where the entire racquet is not strung at hightension, only the longer strings, it is possible to dispense with suchframe reinforcement. This allows manufacture of lighter frames.

The frames may be designed in accordance with the pressure patterns tobe applied, for racquets in accordance with the present invention. Thatis, the strength of the frame will be designed to suit stringingpatterns and requirements for frame characteristics.

It will be appreciated that the stringing method and racquet can be usedfor any type of racquet, e.g., squash, badminton, tennis, racquet balletc.

Present day racquets may be adapted to utilise stringing in accordancewith the present invention. For example, utilising a locking grommetstrip, it is easy to adapt presently available racquets. If cleats arerequired to be used with present racquets, it may be necessary to drillout string holes and make them wider, but it may be done (or,alternatively, mount cleats on the outside of the racquet frame.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

I claim:
 1. A method of stringing a racquet, comprising the steps ofindependently tensioning at least a plurality of strings in the racquetto predetermined tensions and applying means for maintaining theindependent tensioning, wherein the strings are continuously strung, andwherein each individual string of at least the plurality of strings isindependently tensioned against and the tension is maintained by aholding means, the holding means comprising a plurality of cleats intowhich the strings may be locked, the cleats being mounted to a racquetframe, the cleats being V-Jam cleats, comprising opposing side wallsdefining an open top, the walls approaching each other from the openingtowards the bottom of the walls.
 2. A method of stringing a racquetaccording to claim 1, wherein plurality of cleats fixed relative to theracquet frame, each string is strung between a pair of the cleats.
 3. Amethod of stringing a racquet in accordance with claim 2, the step oftensioning each string comprising locking one end of the string in afirst of a pair of the cleats, applying tension to the other end of thestring until the string is tensioned to a predetermined level, and thenlocking the other end of the string in the second of the pair of cleats.4. A method of stringing a racquet in accordance with claim 2,comprising the step of tensioning each string by applying pressure tothe string until the string is tensioned to a predetermined level andthen locking each end of the string within each of the pair of thecleats.
 5. A method of stringing a racquet in accordance with claim 2,wherein the cleats are held by a grommet strip within string holes inthe frame of the racquet.
 6. A method of stringing a racquet inaccordance with claim 2, wherein the cleats are integral with theracquet frame.
 7. A method of stringing a racquet in accordance withclaim 1, wherein the strings are individual strings.
 8. A method ofstringing a racquet in accordance with claim 1, wherein the strings arestrung by a mixture of continuous and individual stringing.
 9. A methodof stringing a racquet in accordance with claim 1, wherein the stringsare provided as a pre-woven mesh, and wherein the method comprises thestep of fitting pre-woven mesh into a racquet frame, tensioning thestrings and maintaining the string tension in the frame.
 10. A method ofstringing a racquet in accordances with claim 9, wherein the step oftensioning the strings comprises adjusting the tension of at least aplurality of the strings at the same time.
 11. A method of stringing aracquet in accordance with claim 1, the method comprising the steps ofapplying tension to the racquet strings in order to implement apredetermined pressure pattern over the face of the racquet.
 12. Asports racquet, strung in accordance with the method of claim
 1. 13. Amethod in accordance with claim 1, wherein a teeth are providedprojecting from the walls of the cleat, the teeth operating to grip aracquet string to tension.
 14. A method in accordance with claim 13,wherein there is a pair of opposing teeth.
 15. A method in accordancewith claim 14, wherein there are a plurality of pairs of opposing teeth.16. A method in accordance with claim 13, wherein the cleats arearranged to be self-locking, whereby the tension of a racquet stringacts against the cleat teeth causing the string to slide further intothe angle of the opposing walls to be locked to tension.
 17. A method inaccordance with claim 16, wherein the teeth comprise angled projectionsprojecting from the opposing walls of each cleat, and lying at an angleso that the foot of the projection, further within the cleat, isdisplaced from the top of the projection, at the opening of the cleat,and, in operation, the cleats are mounted within the racquet so that theteeth angle backwardly from the bottom of the walls to the top in theopposite direction to the direction of tension applied by the strings.18. A sports racquet frame in accordance with claim 17, wherein thereare four or more pairs of opposing teeth.
 19. A method of stringing aracquet, comprising the steps of independently tensioning at least aplurality of strings in the racquet to predetermined tensions andapplying means for maintaining the independent tensioning, wherein thestrings are strung by a mixture of continuous and individual stringing,and wherein each individual string of at least the plurality of stringsis independently tensioned against and the tension is maintained byholding means, the holding means comprising a plurality of cleats intowhich the strings may be locked, the cleats being mounted to a racquetframe, the cleats being V-jam cleats, comprising opposing side wallsdefining an open top, the walls approaching each other from the openingtowards the bottom of the walls.
 20. A method of stringing a racquetaccording to claim 19, wherein the holding means comprises a pluralityof cleats fixed relative to the racquet frame, and each string is strungbetween a pair of the cleats.
 21. A method of stringing a racquet inaccordance with claim 20, the step of tensioning each string comprisinglocking one end of the string in a first of a pair of the cleats,applying tension to the other end of the string until the string istensioned to a predetermined level, and then locking the other end ofthe string in the second of the pair of cleats.
 22. A method ofstringing a racquet in accordance with claim 20, comprising the step oftensioning each string by applying pressure to the string until thestring is tensioned to a predetermined level and then locking each endof the string within each of the pair of the cleats.
 23. A method ofstringing a racquet in accordance with claim 20, wherein the cleats areheld by a grommet strip within string holes in the frame of the racquet.24. A method of stringing a racquet in accordance with claim 20, whereinthe cleats are integral with the racquet frame.
 25. A method ofstringing a racquet in accordance with claim 19, wherein the strings arecontinuously strung.
 26. A method of stringing a racquet in accordancewith claim 19, wherein the strings are individual strings.
 27. A methodof stringing a racquet in accordance with claim 19, wherein the stringsare provided as a pre-woven mesh, and wherein the method comprises thestep of fitting pre-woven mesh into a racquet frame, tensioning thestrings and maintaining the string tension in the frame.
 28. A method ofstringing a racquet in accordance with claim 27, wherein the step oftensioning the strings comprises adjusting the tension of at least aplurality of the strings at the same time.
 29. A method of stringing aracquet in accordance with claim 19, the method comprising the steps ofapplying tension to the racquet strings in order to implement apredetermined pressure pattern over the face of the racquet.
 30. Asports racquet, strung in accordance with the method of claim
 19. 31. Amethod in accordance with claim 19, wherein a teeth are providedprojecting from the walls of the cleat.
 32. A method in accordance withclaim 19, wherein there is a pair of opposing teeth.
 33. A method inaccordance with claim 32, wherein there are a plurality of pairs ofopposing teeth.
 34. A method in accordance with claim 31, wherein thecleats are arranged to be self-locking, whereby the tension of a racquetstring acts against the cleat teeth causing the string to slide furtherinto the angle of the opposing walls to be locked to tension.
 35. Amethod in accordance with claim 34, wherein the teeth comprise angledprojections projecting from the opposing walls of each cleat, and lyingat an angle so that the foot of the projection, further within thecleat, is displaced from the top of the projection, at the opening ofthe cleat, and, in operation, the cleats are mounted within the racquetso that the teeth angle backwardly from the bottom of the walls to thetop in the opposite direction to the direction of tension applied by thestrings.
 36. A sports racquet frame in accordance with claim 35, whereinthere are four or more pairs of opposing teeth.